Yieldable device



Patented June 5, 1945 UNITED STATES" PATENT ori-"ICE mnngnvion Werner F.Boldt, Clayton, Mo., assigner to VWag'- ner Electric Corporationporation of Delaware St. Louis, Mo., a cor- Applicaton September 7,1942, Serial No. 457,603 I 7 Claims.

My invention relates to improvements in" yieldable devices and moreparticularly that type ofV device in which relatively movabletelescoping `cylinders co-ntain a body of non-compressible fluid and abody of compressible uid under pressure with said uids being separatedby a piston.

One of the objects .of my invention is toprovide in a yieldable deviceof the type referred tc, improved means for minimizing leakage of fluidpast the piston in either direction.

Another Aobject of my invention is to provide improved means forpermitting the proper lling of the yieldable device 'with the uids usedtherein. j Other objects ci my invention will become apparent from thefollowing description taken in connection with the accompanying drawingsin which Figure 1 is a View of rmy improved yieldable device showing itbeing used as a strut between a wheel and the body of a vehicle; Figure2 is 'a partial sectional view showing the telescoping arrangement ofthe cylinders; Figure 3 is a sectional view of the lower ends of the.cylinders when they are fully telescoped; Figure 4 is an enlargedsectional View of the piston and socket connection 1 and cylinder 9beingclosed at its lower end by a cap I2 provided with a socket I3 forreceiving ball I4 of the jball and socket connection 6, ysaid ball beingheld in the socket by a platev I5. The external diameter of cylinder 8is somewhat less than the internal diameter of cylinder 9,'thusproducing a chamber I6 between the .walls of the two cylinders.The-lower end of cylinder 8, which is received in cylinder 9, carries asleeve l1 which has such an external diameter as to snugly t in cylinder3 so as to properly guide the lower end of cylinder 8. `This sleeve isprovided with a plurality 1 of circumferentially spaced openings I8 forplacsealing means with the piston'at the extreme l upper end of theinner cylinder; Figure 5 is a sectional view taken on the line 5-5 ofFigure 3; and Figure 6 is a sectional view ci a piston having associatedtherewith a dierent valve'means for aiding the filling of the devicewith the proper volume of non-compressible uid.

Referring. to the drawings in detail and rst to Figure l, I have shownmy improved yieldable device I employed, by way of example, as a strutbetween a wheel of a vehicle and the chassis o1" body thereof. However,it is noted that the de-l vice may be used wherever it is desired tohave a yieldable` support, a suspension device, a rebound controldevice, a shock absorbing device, an energy storing device, and soforth.A As shown in Figure l1, arm 2 is pivoted at one end to a part ofthe chassis or body 3 of a vehicle and its other end has rotatablymounted there# .on a wheel 4. Between arm 2 and another body part 5 ofthe vehicle there is interposed the device or strut I, the connectionbeing Amade by ball and socket connections 6 and 1.

The yieldable ldevice or strut I is shown in Y detail in Figures 2, 3,4, and 5,' reference to which is now made. The strut is composedof twotelescoping cylinders 8 and 9, the former being closed atits 4upper endby a cap I0 provided with a ball II forming Vpart of the ball and ingchamber I6 in communication with the in-K terlor of cylinder 9 below thesleeve.

The upper end of cylinder 9 carries bearing sleeveslx and 20 betweenwhich is interposed suitable annular packing'means 2| to prevent fluidfrom leaking past the two-cylinders yet permitting the cylinders to haverelative axial movement. The bearing sleeves and packingA means are heldin position by a retaining cap 22 secured to the upper end of cylinder9.

Within cylinder B is a piston 23 dividing the space within thetwocylinders into an upper chamber A and a lower chamber' B, the formerbeing solely within cylinder 8 and the' latter within the lower part ofcylinder 8 and the cylinder 9, said chamber B also including the chamberI6 between the walls Vof.' the cylinders. Chamber B is filled withnon-compressible fluid such ascoli or hydraulic brake fluid and chamberA is filled with a compressible fluid or gas',l pref` erably air,under'pressure. Air is admitted into chamber A through an inlet 2B incap I0 which is controlled by an air pressurecheck -valve 25.

, faces toward chamber -A so that it can be acted upon by the fluidunder pressure in the chamber to thus aid in maintaining sealing contactbetween the lip andv the cylinder wall. An ex pander 36 is also shown toaid in the sealing action.- In a like manner the lip 31 of the lower cup33 faces toward chamber B so that the iiuid under pressure in saidchamber can actl upon the lip to thus aid in maintaining it in sealingonly acts as a movable separating wall.

volume of chamber A will increase.

air in chamber A is compressible, it will act as 30 of the vehicle comesdown upon the device as a contact with the cylinder wall. There is alsoprovided an expander 3B for this lip. Ring 3d is provided with anannular groove 3s which receives an ring seal Ml, thereby providingadditional sealingmeans to prevent any transfer of iiuids betweenchambers A and B. The parts 28 and 29 of the piston are so formed as topro. vide a chamber 4i which communicates with a passage 42 extending tothe periphery of the ring 34 at a point between the upper cup 32 and the0 ring.

.`When the chambers A and B are filled with uid with the air in chamberAfunder pressure, the yieldable device or strut will be in operativecondition. Under these conditions the pressures in both chambers are thesame as the piston As the device operates when the vehicle moves,cylinders 8 and 9 will movevrelatively to each other b oth in an` inwardand an outward direction. As cylinder 8 moves inwardly with respect tocylinder 9. piston 23 will be forced upwardly, thus placing the 'a'r inchamber A under additional pressure since thevolume thereof .will bedecreased. When cylinder 8 moves outwardly with respect to cylinder 9,piston 23 will move downwardly with respect to cylinder 8 and the `Sincethe a cushioning means between the wheel and the frame of the vehicleand thus absorb road shocks.

amount of air under pressure in chamber A will slowly leak by thepacking cup y32 and begin to build up 'a' back pressure between the twopacking cups. As this back pressure increases, the sealing action of thecup will decrease (due to pressureon both sides of the lip),` untilthere is a substantial failure thereof, at least such a failure that airwill become mixed with the non-compressible duid in chamber B and thefluid from chamber vB will be mixed with the air in chamber A. This,ofcourse. has been found to be very undesirable since it results in thedeterioration of the oil and improper functioning of the device.The'provision of chamber in' piston 23, which can be called a dead aliichamber, tends to decrease the building up vof this back pressurebetween the two lips and thus dcreases the possibility of leakage pastthe nps tf the cups. rfthe pressurein chamber A should, for example, beabout four hundred pounds per square inch, then as leakage occurs` atthe vlip 35, the air inv chamber 4I willbegin to increase and may reacha pressure even as hlgh as two hundred pounds ing of the strut, asalready pointed out, there will be a drop in the pressure of the air inchamber A when cylinders 8 and 8 move relatively away from each other.If this drop in pressure should be below the pressure of /air in chamber4I., then the pressure in chamber-4I will also drop since air can veryreadily slip by the lip of the cup .back into vchamber A as the cup. haslittle or estarse acts as a means for preventing auch high backpressures building up behind the lips ci the cups that there will beserious leakage. By having the volume of chamber fil substantiallylarge,

d there will be no danger of any rapid build up of back pressure aswould be the case if this chamber werenot present and the leakage ofluid past the cup were coniined to the very small' space at theperiphery of the piston and lying i0 vbetween the cups. The passage 42comunicates with the periphery ofthe piston between the O ring and thelip 35 of cup 32 and operates solely to compensate for the building upof back pressure by leakage of air since a sealing cup 18 will permitleakage of air `more rapidly than leakage of liquid, it being well knownthat a liquidis much easier to seal than a gas such as air. The O ringacts as a safety seal to prevent liquid from passing the piston andsince it func- 20 tions also as a double seal (that is, a seal againstto control the flow of fluid from the lower part of cylinder 8 izo-thelower part of cylnder 8, said conditions being when a considerable forceacts on the device to move the cylinders toward each other as, forexamplel when the'entire weight large obstruction is encountered or whenthe vehicle goes over an embankment. In orderto control the flow of uidbetween the two .cylinder portions of chamber B and prevent `too rapid abuild up of pressure on the bottom of piston 23,

' .there is provided a wall 43 at the lower end of cylinder 8 (shown inFigure 3 wherein the cylinders are in their extreme telescopingpositions).

This wall is held on the cylinder by the bearing o sleeve I1 and isprovided with an opening 44.

4 1n Figure 2, the area of the opening u win be gradually decreased,thus decreasingI the rate of iiow between the lower ends of cylinders 8and 8.

By decreasing the rate of iiow,the downward movement of cylinder 8 willbe slowed up or 5 checked when Vthere is a large'forcel acting to movecylinders 8 and 9 toward cach other, vand the force will not becomeeffective immediately on the piston and air chamber A. The force will Athereby be slowly absorbed.

, Also, in order to check too rapid a separating n movement of cylinders8 and 9, there is provided a ring 48 for cooperation with the upper endsof passages I8 which places the chamber I8 in communication with thelower part of cylinder 8. This. per squarevinch. However, during thefunctionring, as seen in Figures 3 and 5, h as two openings.

41. andwhen fluid tends to flow out of chamber I8 duey to the relativeoutward movement of cylinders l 8 and 8, the ring will seat on top otthe sleeve I1 andV all fluid must now through these two openings .4'|.The ring will have no effect in controlling-the flow of fluid throughpassages I8 when i the cylinder 8 moves inwardly -with respect tocylinder 9 since under these conditions the fluid Y no sealing actionagainst flow of fluid in this` .flowing through passages I8 will liftthe ringoff direction. `Thus the pressure the dead air chamber will becontinuously maintained below the normal pressure in chamber'rA. thatis, theair pressure which is originally placed in the chamber withthe-vehicle at rest. Thus it isv geen that the (leadl all' in the pistonsleeve Il and flow around the ring. The ring in Figure 3 is shown in anunseated position and ensased'with a shoulder 48 for limiting itsunseatingmovement. i l

AI have also p'rovidedneans for facilitating the proper filling ofchamber B withthe nini-ccm-l wardly to their-fullest extent. This may bedone by -merely dropping the wheel over a pin or jacking up the vehicle.Chamber A is then opened tov atmosphere by opening the bleeder plug 49and liquid is forced under a slight pressure into the chamber B throughpassage 26 after removing the plug 21. As chamber B is filled, piston 23will beforced upwardly until it engages cap i at the upper end ofcylinder 8. When the piston is in this position, the lip 31 of cup 33will be over a plurality of circumferentially spaced recesses 50 in thewall of cylinder 8.` Thus the lip cannot seal at these recesses andliquid can ow around the edge of the lip. There is also provided similarcircumferentially spaced recesses which will be opposite the 0 ring 40when the piston is in its extreme upper position so, that liquid lcanpass around this 0 ring. Thuswith thse recessespositioned as shown,`liquid can iiow by all the seals (liquid will slip by lip 35 due to itsposition) and ing-with the stem 51 and the cap BilI is a leaf spring-82which normally biases the valve e'lement 56 Ato seated position. Thehead of the piston Valso has a passage 63 to facilitate the now 4of duidfrom one side ofthe -head to the other when the4 valve element 53 isunseated.

With the valve arrangement shown it is obvious that during the fillingoperation when chamber B is led with liquid under a slight pressure,

.ment 56 is seated. When the piston reaches the out by way of thebleeder plug as liquid is forced 49 is closed. During this fillingoperation a small amount of liquid will get into the bottom of chamber Mbut this will not be harmful as the major portion of the chamber willstill be filled with air.

Air under pressure is now forced into chamber A through valve 25. Thiswill cause piston 23 to be moved downwardly and push liquid out 'ofpassage 26. Air will not pass the piston under these conditions becausethe lip of the sealing cup 33 functions to'prevent passage of air sincethere is no recess underneath this lip. As the piston initially movesdownwardly, the O ring will pass -below the recesses 5B and 5i andfunction as a seal so as to prevent air from passing the piston when lip35 of cup t2 passes the recesses-50 and 5|. Air under pressure is placedin chamber A until piston 23 engages wall t3 at the lower end ofcylinder 8. passage 26 is closed by the filler plug 21. The -device willnow contain the proper amount of noncompressible fluid. Air underpressure is continued to be placed in chamber A until it reaches thedesired predetermined pressure which will depend upon how high it isdesired to have the vehicle frame above the roadway and also thetemperature conditions under A'which the de- When this occurs, Y

vice is to be operated. When the device is used for each-wheel, theamount of ai'r in each chamber A is such that the vehicle will be levelwhen the wheels are on a level roadway.

In Figure 6 I have shown a slightly modifiedthe piston there is asealing disc 58 vhaving aiip portion 59 cooperating with the stem topreventv fluid from flowing back through passage 54 but not preventing`fluid from flowing in the opposite direction aroundthe stem.Arperforated cap 60 rests on top of the sealingdisc 58. The sealingdisc, the cap and the valve seat 55. are all held on the head of thepiston by bolts 67|. Cooperat- .top of cylinder 8; stem 51 will engagecap I0,

thereby -unseating `valve element 55 and permitting liquid in chamber Bto iiow out through chamber-f A and the bleeder plug and thus expel alltheair. vAfter the bleeder plug is closed and air under pressure isforced into chamber A causing the piston to move downwardly, valve 56will automatically become seated as soon as there is initial movement ofthe piston since spring 62 can then come into action to performV theseating operation. The lip 59 of the sealing disc 58 will prevent airfrom passing around stem 5'1 and, ofcourse, fluid cannot pass fromchamber B to chamber A vbecause' valve element 56 is seated. Thepressure in chamber B will continue to hol'i valveeiement't seated sinceit acts upon a larger area than the cross-sectional area of the stemwhich is subject to a like pressure in chamber A. When piston 23'reaches the lower end of cylinder t, chamber B is sealed and additionalair under pressure is put into chamber A.

Being aware-of Vthe possibility of modifications in theparticularvstructure herein described withf out departing-imm thefundamental principles of my invention," I do not intend that its: scopebe lim except asset forth by the appended claims. i

IIi'iaving"'fully described my invention, what I claim as new and desiret0 secure by Letters Patent of the United States is: n

l.. In a device having a cylinder and a piston capable of relativemovement and in which the piston is subject m a compressible gas underpressure' onione side and to a non-compressible duid under pressure onthe other side, a sealing cup carried by the piston and having a sealinglip subject to the pressure of the gas, means forming a dead gas chamberof substantial volume for movement with the piston, means for placingthe chamber in constant communication with the rear of said cup, andother sealing means carried by the piston. for preventing4 thenon-compresslble uid from entering the chamber or the gas from mixingwith the non-compressible fluid.

2. I n a device having a cylinder and Aa piston capable of relativemovement and in which the piston is subject to fluid pressures onopposite sides thereof, a sealing cup carried by the piston and having alip extending toward one end of the piston and subject to the pressureeffective on that end of the piston to thereby assist in maintaining asealing action with the cylinder wall tp prevent fluid from `flowingpast the piston :from said one end but permitting fluid to flow pastsaid lip to the said one end, a chamber of substantial volume formedwithin the piston and in constant communication with the space at therear o1' the lip, an axially spaced sealing cup carried by the pistonand having its lip exposed to the pressure effective on the 'other endof the piston, and an 0 ring sealing means between the rear of the lastnamed cup and the chamber. 3. In a yieldable device of the classdescribed,

l, two telescoping cylinders closed at their outer ends, a pistonpositioned in onel cylinder and dividing the space within the cylindersinto two chambers, a non-compressible uid in one chamber, a compressibleduid under pressure in the other chamber, axially spaced sealing cupscarried by the piston, said cups being provided with y sealinglipscooperating with the cylinder wall and arranged so that the cupadjacenteach chamber will have its lip acted upon by iiuid pressure inthat chamber to thereby aid in maintaining sealing contact, meansforming a third chamber` of substantial volume in the piston, means forpiacing said third chamber in communication chambers, said piston havingna normal operating with the peripheral part of the piston between thetwo sealing means, and a seal for preventing fluid from iiowing from thethird chamber to the rear of the lip of Athe cup adjacent; the chambercontaining the nonfcompressible iiuid.

4. In a device having-a cylinder anda relatively movable lpiston thereinproviding separated range of relative movement remote from the ends ofthecylinder, iiuid in both chambers, the fluid in at least, one of thechambers being in the form of 'a liquid, a plurality of sealing meansfor the piston for preventing interchange of iiuid between the chambers,and the chamberwalls of one of said chambers having recess means formedtherel in for permitting liquid from said liquid contain--V ing chamberto by-pa'ss the piston and its sealing means only when the piston ispositioned at f the end of the cylinder remote from the liquidcontaining chamber, said sealing means preventing any return flow of uidto the liquid containing chamber when the piston is in any otherposition in the cylinder and regardless of differential der walls havingrecess means formed thereinA operable only when the piston is at theclosed estates permitting the non-compressible duid to lay-pass thepiston and its sealing means, said sealing means preventing compressiblenuid from passing the piston in either direction when it is in aposition remote-from said closed end ot'. the cylinder and'regardless ofdifferential pressures existing on opposite sides of the piston.

'6. In adevice having a cylinder and a relatively movable piston thereinproviding separated chambers, said piston having a normal operatingrange of relative movement remote from the ends of the cylinder, fluidin both chambers, the fluid in at least one of the chambers being in theform of a liquid, twoaxially spaced sealing cups carried by the piston,said sealing cups having lips projecting toward opposite endsof thepiston, and means comprising a recess in the wall of the cylinder forpermitting liquid to pass the lip of that cup for that end of the pistonacted upon bythe. liquid but only when the piston isy moved to theendgoi the cylinder which is at that side of the piston opposite theliquid containing end of the cylinder in which it is positioned forchamber, and when said sealing means for said liquid is opposite saidrecess.

7. In. a device having a cylinder and a relatively movable pistontherein providing separated chambers, said piston having a normaloperating range oi relative movement remote from` the ends of thecylinder, uid inl both chambers, the fluid in at least one of thechambers beingv in the form of a liquid, two axially spaced sealing cupscarried by the piston, said sealing cups having lips projecting towardopposite ends or the piston,

an 0 ring sealing means carried by the pistonv between'the cups; andmeans comprising recesses in the wall of the cylinder cooperating withthe lip of the cup sealing the liquid side of the piston and with the 0ring but only when`the'piston is at one end of the cylinder to therebypermit liquid to by-pass the".` piston, said recesses .and the` WERNERF. BoLDT.4

